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64- CHAPTER 3 1953', Guide Absolute Temperature Gravity Density 518.4 F Abs '32.1740 ft per (see) (sec) 0.07651 lb per cu ft .Values of pressure and temperature are listed in Table 6 for altitudes in the standard atmosphere from --1000 to 50,000 ft above sea level. For further explanation, References 9 and 10 should be consulted. LETTER SYMBOLS USED EST CHAPTER 3 , M = degree of saturation (decimal). p = density of fluid, pounds per cubic foot. <p = relative humidity (decimal). a = ratio of apparent molecular weight of dry air (28.966) to the molecular weight of water (18.016) = 1.6078. A = coefficient from Table 5 for use in Equation 30 (obtained from Table 5). B = coefficient to be used in Equation 31 (obtained from Table 5). C = coefficient for use in Equation 32 (obtained from Table 5). ' fu -- factor accounting for effect of mixing air and water, dimensionless. G -- flow rate of dry air, pounds per hour. _ Gi =` flow rate of dry air, pounds per minute. - ------ Gw = rate of evaporation of water, pounds per minute. H enthalpy of the system. B = enthalpy of the flowing medium, Btu per pound of dry air; A = enthalpy of moist air, Btu per pound of dry air. A = enthalpy correction term to be added above 150 F, to enthalpy. = specific enthalpy of dry air, Btu per pound. An = A, -- ho ' = the difference between the enthalpy of moist air of saturation per pound of dry air, and the specific enthalpy of the dry air itself, Btu per pound of dry air. A = enthalpy of saturated water vapor, Btu per pound. hr. = enthalpy of moist air at saturation per pound of dry air, Btu per pound of dry air. h* = enthalpy of moist air at saturation at thermodynamic wet-bulb temperature ' Btu per pound of dry air. . Aw = specific enthalpy of condensed water (liquid or solid) at standard pressure ' Btu per pound water. ' Aw* = specific enthalpy of water as added at the thermodynamic wet-bulb temperature f*. Btu per pound of dry air. Awi = enthalpy of liquid water, Btu per pound. Aw. = enthalpy of solid water, Btu per pound. KE = average kinetic energy, Btu per pound. KE = average kinetic energy, Btu per pound. L = flow rate of liquid water, pounds per hour. to = weight of dry air crossing any duct section, pounds per minute. n. = mols dry air. ns = mols of water vapor at saturation, n. = mols of water vapor. P = absolute pressure. P, = atmospheric pressure, inches Hg. Thermodynamics 65 LETTER SYMBOLS (Continued) Po ,,= standard atmospheric pressure by definition 29.921 in; Hg. P, = saturation pressure of pure water at prevailing temperature. . p = total pressure of a mixture of air and water vapor, pounds per square inch . or inches Hg. - p. = partial pressure of dry air, pounds per square inch or inches Hg. p, = saturation pressure of pure water vapor, pounds per square inch or inches Kg- p. = partial pressure of water vapor in mixture of air and water vapor, pounds per square inch or inches Hg. PE = .potential energy, Btu per pound dry air. PE = average potential energy, Btu per pound dry air. Q = total heat added or subtracted, between sections, Btu per minute. q = ratio of energy added (or removed) to water added (or removed), Btu per pound. Also called specific enthalpy of water, added. ,q, -- energy added between points 1 and 2. ,q2 = heat added between sections 1 and 2, Btu per pound dry air. . H = universal gas constant, 1545 foot-pounds per (Fahrenheit degree), (mol). Ro = gas constant for' dry air. R = gas constant for water vapor. S = flow rate of solid water, pounds per hour. i s = entropy of moist air per pound of dry air, Btu per (pound) (Fahrenheit degree). S -- correction to be added to entropy of moist air obtained from Table 2. i = additional correction to be added to entropy because of "mixing entropy" (obtained from Table 5). Correction to be added to value of 8 obtained from Table 2. s, = specific entropy of dry air, Btu per (pound) (Fahrenheit degree, absolute). 8.. = the difference between the entropy of moist air at saturation per pound of dry air, and the specific entropy of the dry air itself, Btu per (pound of dry air); (Fahrenheit degree; absolute), s. = entropy of moist air at saturation per pound of dry air, Btu per (pound of dry air) (Fahrenheit degree, absolute). sw = specific entropy of condensed water (liquid or solid) at standard atmos pheric pressure, Btu per (pound of water) (Fahrenheit degree, absolute). T = absolute temperature, Fahrenheit degrees. T0 = standard atmospheric temperature, by definition 518.4 F absolute. t = temperature, Fahrenheit degrees. t* = thermodynamic wet-bulb temperature, Fahrenheit degrees. U = internal energy of system. U = internal energy. V = volume. F = average velocity, feet per minute. v = volume of moist air per pound of dry air, cubic feet per pound. = correction to be added to volume of moist air per pound of dry air, above. 150 F. Vo -- specific volume of dry air, cubic feet per pound.